Hybrid dry air cooling system

ABSTRACT

A method and system for an air conditioning system, wherein the air conditioning system uses both a dry ambient air cooling system and a mechanical refrigeration system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and incorporates, for all purposes, the subject matter of U.S. Provisional Patent Application Ser. No. 62/361,453, filed on Jul. 12, 2016.

BACKGROUND

This disclosure relates generally to large-scale Heating, Ventilation, and Air Conditioning (HVAC) systems, which in some embodiments, may be employed to provide cooling for computer-system data centers and other large structures which may contain or produce an excess of heat.

Large-scale data centers typically house a variety of computer systems in a common facility. Data centers may also house associated components such as telecommunication and data storage systems and backup units such as power supplies, data communication connections, etc. The various computer, data storage, telecommunication, power and other systems at a data center may generate significant amounts of heat. Moreover, the various systems of a data center are typically arranged with minimal spacing to reduce land and building costs. Locating a large number of such heat-generating systems and components in one location and in close proximity to each another can create heat dissipation issues. Mechanical, compressor-based, HVAC cooling systems are often used to ensure that the computer systems operate within safe operating temperatures.

Mechanical, compressor-based HVAC cooling systems may use large amounts of electrical power, diesel, natural gas, or the like, to power compressors as part of a refrigeration cycle.

HVAC systems also often consume immense amounts of water. For example, many large-scale HVAC cooling systems, like those used at data centers, employ cooling towers that use water-based evaporative cooling, also referred to as a water-side economizer, to pre-cool water, propylene glycol, or a heat transfer fluid before the heat transfer fluid may be further cooled by a mechanical compressor-based refrigerator or chiller. Water-based evaporative cooling is attractive, because water has a relatively high energy density (energy/unit volume) compared to a large number of elements and compounds and because water also has a large enthalpy of vaporization (energy required to change from liquid phase to gaseous phase).

However, a data center using an HVAC cooling mechanism with water-based evaporative cooling towers may consume large volumes of water on a daily, monthly, or annual basis. Water is becoming less available and more expensive. Use of water is now also understood to impose significant burdens on the environment.

When ambient external air temperatures fall below the temperature of air in a building, air-side economizers are sometimes used to reduce energy consumed by mechanical HVAC systems. In a simple form, an open window can be understood as an air-side economizer, as it may let cool ambient air into the warm air of the building. However, air handling systems in many contemporary buildings, such as computer system data-centers, hospitals, and the like, often filter air to remove dust, smoke, pollution, corrosive compounds, allergens, and biologically active material or organisms. In such a context, simply “opening a window” is not desirable. More complex air-side economizers incorporate air filters or may use a heat exchanger to exchange heat between air in the building and ambient external air. When the temperature of heat transfer fluid exiting a process cooling system is below ambient air temperatures, legacy air-side economizers are not used, because the ambient air would be warming the heat transfer fluid, instead of cooling it.

Mechanical HVAC cooling system are commonly designed to operate with a minimum “head pressure” in a condenser, such that condenser coils avoid a “low load” condition. Low load conditions can result in laminar flow in a condenser, underfeeding of thermostatic expansion valves, and oil logging (when oil logs in an evaporator), all of which negatively impact efficiency and/or the operating life of the machinery.

Embodiments will be readily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements. Embodiments are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an example of an embodiment of a hybrid dry air cooling system.

FIG. 2 is a schematic diagram illustrating a first example of an embodiment of a hybrid dry air cooling system.

FIG. 3A is a first portion of a flow chart illustrating an example of an embodiment of a process performed by a control system of a hybrid dry air cooling system.

FIG. 3B is a second portion of a flow chart illustrating an example of an embodiment of a process performed by a control system of a hybrid dry air cooling system.

FIG. 4 is a schematic diagram illustrating a second example of an embodiment of a hybrid dry air cooling system.

FIG. 5 is a schematic diagram illustrating a third example of an embodiment of a hybrid dry air cooling system.

FIG. 6 is a functional block diagram illustrating an example of a computer device incorporated with teachings of the present disclosure, according to some embodiments.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the examples, sometimes referred to as embodiments, illustrated and/or described herein. These are intended merely as examples. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Alterations and further modifications in the described processes, systems or devices, any further applications of the principles of the invention as described herein, are contemplated as would normally occur to one skilled in the art to which the invention relates, now and/or in the future in light of this document.

In overview, a hybrid dry air cooling system is disclosed herein, connected to a cooled space, such as a building. The hybrid dry air cooling system comprises a dry ambient air cooling system, a control system, a mechanical refrigeration system, and an air handling unit, coupled to a cooled space.

In overview, the dry ambient air cooling system comprises a closed-loop of heat transfer fluid, a heat transfer fluid/external-air heat exchanger (which exchanges heat energy between heat transfer fluid and external air; this is also referred to as a heat rejection coil) coupled to the closed-loop of heat transfer fluid, one or more fans or blowers, and a partially enclosed air space, enclosing the heat transfer fluid/external-air heat exchanger. The partially enclosed air space is open to ambient outside air, and coupled to the blowers, such that the blowers can pull or push ambient outside air across the heat transfer fluid/external-air heat exchanger.

The dry ambient air cooling system is used by the control system, not to directly cool air in the cooled space, but to cool heat transfer fluid of the refrigeration system. When ambient outside air is cool enough, the control system uses the dry ambient air cooling system to cool heat transfer fluid of the mechanical refrigeration system in the heat transfer fluid/external-air heat exchanger.

The hybrid dry air cooling system also comprises the mechanical refrigeration system. The mechanical refrigeration system may comprise, for example, a mechanical compressor, a closed-loop of pipe, conduit, or the like containing a phase-transition refrigerant, an external air/phase-transition refrigerant heat exchanger (to exchange heat energy between external air and phase-transition refrigerant; this component is also referred to herein as a condenser coil), thermal expansion valve, and a heat transfer fluid/phase-transition refrigerant heat exchanger (to exchange heat energy between heat transfer fluid and phase-transition refrigerant). Examples of phase-transition refrigerants include ammonia, methyl chloride, propane, chlorofluorocarbon, dichlorodifluoromethane, chloromethane, and the like. Compressed phase-transition refrigerant is allowed to expand or otherwise transition from a liquid phase to a gas phase in heat transfer fluid/phase-transition refrigerant heat exchanger, drawing heat energy out of heat transfer fluid and transferring heat energy of the heat transfer fluid to the phase-transition refrigerant. The warm or hot gas phase form of the phase-transition refrigerant is then compressed by compressor in external air/phase-transition refrigerant heat exchanger into a liquid or compressed form, releasing heat energy to external ambient air, and returning as a liquid to thermal expansion valve and heat transfer fluid/phase-transition fluid heat exchanger. In an embodiment disclosed herein, external air/phase-transition refrigerant heat exchanger of the mechanical refrigeration system is downstream of the heat transfer fluid/external-air heat exchanger (or heat rejection coil) of dry ambient air cooling system.

The hybrid dry air cooling system also comprises a heat transfer fluid/internal-air heat exchanger, to exchange heat energy between the heat transfer fluid and return air of an air handling unit. This may also be referred to herein as a “process air heat exchanger” or “cooling manifold” and may be described as being part of an “air handling unit”. The hybrid dry air cooling system also comprise the air handling unit. The air handling unit obtains warm air from inside the cooled volume, also referred to herein as “return air”, and passes the return air across the heat transfer fluid/internal-air heat exchanger, such that heat energy passes from the return air to the heat transfer fluid/internal-air heat exchanger and to the heat transfer fluid. The heat transfer fluid, now warmed by the return air, is cooled by a control system, using the dry ambient cooling system and/or the refrigeration system, as discussed further herein. The cooled return air, now referred to as “supply air”, is then returned to the cooled volume by the air handling unit.

The air handling unit may also comprise air filters, dehumidifiers, and the like, to maintain a desired air purity and humidity level inside the cooled volume. Effort may be expended to limit direct mixing between external ambient air and interior air of the cooled space.

The hybrid dry air cooling system also comprises the control system. The control system monitors the external ambient air, generally measuring temperature and/or humidity, which may also be described as a measurement of enthalpy of the external ambient air. When external ambient air is cool and dry enough (or when the enthalpy of the external ambient air is low enough), the control system preferentially uses the dry ambient cooling system to cool the heat transfer fluid in the closed-loop of heat transfer fluid. If the dry ambient cooling system is not able to cool the heat transfer fluid enough to meet supply air requirements, the control system may engage the compressor-based refrigeration system to mechanically cool or chill the heat transfer fluid.

The control system of the hybrid dry air cooling system may seek to maintain a relatively high temperature of heat transfer fluid exiting heat transfer fluid/internal-air heat exchanger, such as at an upper limit of an allowed range. The control system may perform this by i) adjusting use of the dry ambient cooling system relative to use of the mechanical refrigeration system, preferentially increasing use of the dry ambient cooling system when excess cooling capacity remains in the dry ambient cooling system and/or by ii) reducing a volume of heat transfer fluid flowing to the heat transfer fluid/internal-air heat exchanger. It is not known or suggested to maintain a relatively high temperature of heat transfer fluid exiting heat transfer fluid/internal-air heat exchanger and/or it is not known or suggested to use of these two factors (preferential use of a dry ambient cooling system and reduction in mass flow rate of heat transfer fluid into heat transfer fluid/internal-air heat exchanger) to maintain a relatively high temperature of heat transfer fluid exiting heat transfer fluid/internal-air heat exchanger, such as at the top end of an allowed temperature range.

Reduction in the volume of heat transfer fluid flowing to the heat transfer fluid/internal-air heat exchanger may be performed by reducing the overall flow rate within the closed loop of heat transfer fluid. However, in order to maintain a minimum required system pressure, such as a minimum pressure required to operate control valves and/or heat exchangers, the volume of heat transfer fluid flowing to the heat transfer fluid/internal-air heat exchanger may be reduced, with a resulting bypass fluid being mixed with heat transfer fluid outside of the heat transfer fluid/internal-air heat exchanger, and with this portion of heat transfer fluid (outside of the heat transfer fluid/internal-air heat exchanger), being held at or above the minimum required system flow rate.

By maintaining a relatively high temperature of heat transfer fluid exiting heat transfer fluid/internal-air heat exchanger, the hybrid dry air cooling system may continue to use the dry ambient cooling system to address at least part of the cooling load when the temperature of ambient air is less than the temperature of heat transfer fluid exiting heat transfer fluid/internal-air heat exchanger.

In contrast, legacy cooling systems typically maintain a constant mass flow rate of heat transfer fluid into and out of the heat transfer fluid/internal-air heat exchanger or process cooling system. In, for example, low load conditions or during times of ambient air temperature swings, legacy cooling systems with a constant mass flow rate may produce heat transfer fluid exiting the heat transfer fluid/internal-air heat exchanger below the temperature of ambient air. In such cases, a dry ambient cooling system or a “free energy” system cannot be used and mechanical cooling or water chilling must be used to address all of the cooling load, even if the ambient air is cooler than the upper end of an allowed temperature range for heat transfer fluid exiting the heat transfer fluid/internal-air heat exchanger (because the temperature of ambient air is below the temperature of heat transfer fluid exiting the heat transfer fluid/internal-air heat exchanger). Producing heat transfer fluid exiting the heat transfer fluid/internal-air heat exchanger below the temperature of ambient air thereby results in unnecessary use of relatively expensive mechanical cooling or water chillers. By varying the flow rate of heat transfer fluid into the heat transfer fluid/internal-air heat exchanger to keep the heat transfer fluid which exits the heat transfer fluid/internal-air heat exchanger at the top end of an allowed temperature range, the disclosed hybrid dry air cooling system can continue to use the relatively economical dry ambient cooling system to address at least part of the cooling load.

FIG. 1 is a block diagram of an implementation of a hybrid dry air cooling system 100 that may provide hybrid air- and mechanical-cooling within a building or other space, which may be referred to as cooled volume 105. In embodiments, cooled volume 105 may include a building or data center room. The building or data center room may contain a variety of computer systems, or may be or include another type of commercial or industrial space, or may be or include a residence or a temporary space or structure, such as a tent.

Hybrid dry air cooling system 100 may include air handling unit 110, also referred to herein as a process cooling system, which may be in fluid-communication with cooled volume 105 such that warm return air from within cooled volume 105 may be drawn through air handling unit 110, passed across a cooling manifold or heat transfer fluid/internal-air heat exchanger of air handling unit 110 (as described below in greater detail), and returned to cooled volume 105 as supply air at a lower temperature relative to the warm return air. Cooling system 100 may further include dry ambient cooling system 115, refrigeration system 120, a cooling mixer 125 coupled between dry ambient cooling system 115 and refrigeration system 120, a mass flow rate controller 126 controlling a volume of heat transfer fluid flowing to cooling manifold or heat transfer fluid/internal-air heat exchanger of air handling unit 110, and a control system 130 coupled to i) cooling mixer 125 to control reciprocally proportional cooling provided by dry ambient cooling system 115 and refrigeration system 120 and coupled to ii) mass flow rate controller 126 to maintain a relatively high temperature of heat transfer fluid exiting heat transfer fluid/internal-air heat exchanger, such as at the top end of an allowed temperature range. In FIG. 1, mass flow rate controller 126 is illustrated as between refrigeration system 120 and air handling unit 110 (along the input path to air handling unit 110) and separate from mixer 125. In embodiments, mass flow rate controller 126 may be a component, such as a valve, of mixer 125 and may be located along the output path from air handling unit 110. Mass flow rate controller 126 may also be or include a variable pump that circulates heat transfer fluid 135. Embodiments of components found in air handling unit 110, dry ambient cooling system 115, and refrigeration system 120 are illustrated and discussed in FIGS. 2, 4, and 5.

Hybrid cooling system 100 may utilize a closed-loop containing heat transfer fluid 135. Heat transfer fluid 135 may be or comprise, for example, water, propylene glycol, or the like. In embodiments, heat transfer fluid 135 may be a solution comprising water and propylene glycol (e.g., 10-30%). It will be appreciated, however, that many other heat transfer fluids may be used. Heat transfer fluid 135 may circulate in the closed-loop, such as by operation of pumps or passively, between air handling unit 110, dry ambient cooling system 115, and refrigeration system 120. Closed-loop heat transfer fluid 135 may pass through heat transfer fluid/internal-air heat exchanger of air handling unit 110. Warm return air from cooled volume 105 may be passed across the heat transfer fluid/internal-air heat exchanger of air handling unit 110, to reduce the temperature of the warm return air and to produce lower-temperature supply air to be supplied to cooled volume 105. The heat transfer fluid/internal-air heat exchanger of air handling unit 110 transfers heat from the warm return air of cooled volume 105 to heat transfer fluid 135.

Heat from warm return air of cooled volume 105, after transfer to heat transfer fluid 135, may be transferred externally, such as outside to external ambient air, via dry ambient cooling system 115 and/or refrigeration system 120. Dry ambient cooling system 115 may be characterized in that it employs dry ambient air, rather than evaporation of water or a mechanical refrigeration system, to cool heat transfer fluid 135. Refrigeration system 120 may be characterized in that it employs variable capacity mechanical cooling to provide cooling of heat transfer fluid 135.

In embodiments, dry ambient cooling system 115 may selectively provide dry cooling and/or precooling of heat transfer fluid 135 of hybrid cooling system 100 according to operation of control system 130 and the ambient air temperature and/or humidity, without application of water for evaporative cooling. Although embodiments may selectively further employ wet evaporative cooling under some severe ambient conditions, such wet evaporative cooling would supplement the dry ambient cooling of dry ambient cooling system 115.

In embodiments, hybrid cooling system 100 may further control a mass flow rate of heat transfer fluid 135 to heat transfer fluid/internal-air heat exchanger of air handling unit 110, according to operation of control system 130, to maintain a temperature of the heat transfer fluid 135 flowing out of cooling manifold and heat transfer fluid/internal-air heat exchanger of air handling unit 110 close to or at an upper limit.

As an example illustrating operation of one implementation, hybrid cooling system 100 may be operated to receive return air at air handling unit 110 from cooled volume 105, wherein the return air has a temperature of about 100° F. Hybrid cooling system 100 may provide to cooled volume 105 via air handling unit 110 supply air having a temperature of about 79.8° F. In this example, heat transfer fluid 135 may enter air handling unit 110 at a cooling temperature of about 75.1° F. and may return from air handling unit 110 at a heated temperature of about 88.1° F. The heated temperature of about 88.1° F. may be an upper limit of an allowed range for heat transfer fluid 135 exiting air handling unit 110. In operation, control system 130 may selectively employ dry ambient cooling system 115 and/or refrigeration system 120 to return heat transfer fluid 135 to the cooling temperature of about 75.1° F. to be recirculated through air handling unit 110.

In operation, control system 130 may selectively increase or decrease a mass flow rate of heat transfer fluid 135 flowing into and out of air handling unit 110 and heat transfer fluid/internal-air heat exchanger of air handling unit 110 to maintain the relatively high temperature of heat transfer fluid 135 exiting heat transfer fluid/internal-air heat exchanger of air handling unit 110, for example, at the upper limit of the allowed range. Maintaining the heat transfer fluid 135 exiting heat transfer fluid/internal-air heat exchanger of air handling unit 110 at the upper limit allows hybrid dry air cooling system 100 to continue to use dry ambient cooling system 115. For example, in a low-load condition, a constant mass flow rate of heat transfer fluid 135 through air handling unit 110 might result in a temperature of heat transfer fluid 135 exiting air handling unit 110 of 84 degrees. In this example, if ambient external air has a temperature of 85 degrees (warmer than the temperature of heat transfer fluid 135 exiting air handling unit 110), cooling from a mechanical chiller or a water chiller would be required without any cooling provided by dry ambient cooling system 115, resulting in unnecessary consumption of energy and/or water.

Typically, dry ambient cooling system 115 may operate with lower power requirements than refrigeration system 120, so that control system 130 may preferentially employ dry ambient cooling system 115 over refrigeration system 120, to the extent that the temperature of ambient (e.g., outside) air used to provide cooling of the dry ambient cooling system 115 can provide sufficient cooling. However, as the temperature and/or humidity of the external, outside, ambient air increases, control system 130 may further employ cooling by refrigeration system 120 to cool heat transfer fluid 135, for example, to cool heat transfer fluid 135 to, e.g., 75.1° F. Under, for example, low or intermediate load conditions or at times during a day of temperature swings (such as at morning or evening), control system 130 may decrease a volume of heat transfer fluid flowing into and out of air handling unit 110 and heat transfer fluid/internal-air heat exchanger of air handling unit 110 to maintain the temperature of heat transfer fluid flowing out of air handling unit 110 at the allowed upper limit of a range. Low or intermediate load conditions may occur, for example, when there is reduced heat production within cooled volume 105.

FIG. 2 is a schematic diagram of a first implementation of components of hybrid dry air cooling system 200. It will be appreciated that the implementation of FIG. 2 is illustrative and that many other implementations and configurations may be employed. For example, FIG. 4 illustrates a second implementation of components of a hybrid dry air cooling system 400 and FIG. 5 illustrates a third implementation of components of a hybrid dry air cooling system 500. Hybrid dry air cooling system 200 may be characterized relative to hybrid dry air cooling system 400 and hybrid dry air cooling system 500 in that hybrid dry air cooling system 200 may not vary a flow rate of heat transfer fluid into air handling unit 110 (and a heat transfer fluid/internal-air heat exchanger thereof), whereas hybrid dry air cooling system 400 and hybrid dry air cooling system 500 may vary the flow rate of heat transfer fluid into air handling unit 110 (and a heat transfer fluid/internal-air heat exchanger thereof).

As illustrated in FIG. 2, air handling unit 110 may include one or more blowers or fans 205 that may draw warm return air 210 from within cooled volume 105 (FIG. 1) across or through a cooling manifold or heat transfer fluid/internal-air heat exchanger 215. Heat transfer fluid/internal-air heat exchanger 215 may be coupled to a closed loop of heat transfer fluid 235 and to the return air 210. Heat transfer fluid 235 is an example of heat transfer fluid 135 of FIG. 1. Heat transfer fluid/internal-air heat exchanger 215 may thereby cool the return air 210 using heat transfer fluid 235, producing cooled supply air 220. Supply air 220 may then be returned to cooled volume 105 by fans 205, at a temperature lower than return air 210.

Pump 225 may operate to circulate heat transfer fluid 235 through its closed loop toward dry ambient cooling system 115 and refrigeration system 120.

Control system 231 is an example of control system 130 in FIG. 1. Control system 231 in FIG. 2 is illustrated as connecting to output and input components via electrical, data, pneumatic, or physical lines (illustrated with broken lines), Control system 231 may be coupled to and control operation of mixing valve 236. With reference to FIG. 1, mixing valve 236 may operate as mixer 125. For example, mixing valve 236 may be selectively operated by control system 231 so that a heat transfer fluid portion 235A of heat transfer fluid 235 may pass through dry ambient cooling system 115 and/or a heat transfer fluid portion 235B of heat transfer fluid 235 may pass through a bypass 230 that bypasses ambient cooling system 115, as described herein in greater detail. Control system 231 may include one or more temperature sensors 138A, 138B, 138C, 138D for example, that may provide temperature readings from which control system 231 may control proportional and/or relative operation or use of dry ambient cooling system 115 and refrigeration system 120.

Dry ambient cooling system 115 may include one or more blowers or fans 240 that may draw ambient (e.g., outside) external air 245 across or through a heat transfer fluid/external-air heat exchanger 250 (e.g., a heat rejection coil or cooling manifold). Heat transfer fluid/external-air heat exchanger 250 may be coupled to the closed loop of heat transfer fluid 235 to receive heat transfer fluid portion 235A and so may provide cooling of heat transfer fluid 235 that is carrying heat from warmed return air 210 from cooled volume 105 (FIG. 1). After passing across heat transfer fluid/external-air heat exchanger 250, the ambient external air 245 may be vented out or returned as return ambient air 255. Temperature sensor 138A may sense or measure the temperature of ambient (e.g., outside) external air 245, and temperature sensor 138B may sense or measure the temperature of heat transfer fluid 235 passing out of air handling unit 110.

In some embodiments and/or under some conditions, control system 231 may operate mixing valve 236 to direct some or all of heat transfer fluid 235 as heat transfer fluid portion 235A passing through dry ambient cooling system 115 or may operate mixing valve 236 to direct some or all of heat transfer fluid 235 as heat transfer fluid portion 235B passing through bypass 230. The mass flow rate of heat transfer fluid 235 may remain constant and may be of the combined flow rates heat transfer fluid portions 235A and 235B. For example, control system 231 may operate mixing valve 236 to direct all of heat transfer fluid 235 as heat transfer fluid portion 235B passing through bypass 230 if the temperature or enthalpy of ambient (e.g., outside) external air 245 measured by temperature sensor 138A is greater than the temperature of heat transfer fluid 235 measured by temperature sensor 138B.

In other embodiments and/or under other conditions, control system 231 may operate mixing valve 236 to modulate or trim the proportions of heat transfer fluid portion 235A and heat transfer fluid portion 235B, as the volumetric flow rate of heat transfer fluid 235 remains constant, when the temperature of cooling ambient (e.g., outside) external air 245 measured by temperature sensor 138A is low enough that ambient cooling system 115 has more cooling capacity than is needed to adequately cool heat transfer fluid 235. In these circumstances, for example, flow rate or proportion of heat transfer fluid portion 235A entering ambient cooling system 115 may be increased and the flow rate or proportion of heat transfer fluid portion 235B entering bypass 230 may be decreased as the temperature of ambient (e.g., outside) external air 245 measured by temperature sensor 138A decreases to provide adequate cooling of the coincident process heat load that heat transfer fluid/internal-air heat exchanger 215 absorbs from cooled volume 105. The heat transfer fluid 235 mass flow rate shall be sufficient to cool the coincident process heat load in cooled volume 105.

In embodiments, dry ambient cooling system 115 may further include an optional external air/phase-transition refrigerant heat exchanger 260 (also referred to as a “condenser coil 260”), which may operate when the heat absorbed by the heat transfer fluid 235 in heat transfer fluid/internal-air heat exchanger 215 is not rejected in its entirety by the flow of external air 245 over heat transfer fluid/external-air heat exchanger 250. Control system 231 may control the mass flow rate of external air 245 with fan(s) 240, which may vary the mass flow rate of external air 245 entering i) heat transfer fluid/external-air heat exchanger 250 and ii) external air/phase-transition refrigerant heat exchanger or condenser coil 260.

When the heat transfer fluid portion 235A leaving the heat transfer fluid/external-air heat exchanger 250 is of insufficiently low temperature to absorb the process heat load in cooled volume 105 transferred by heat transfer fluid/internal-air heat exchanger 215, further required temperature reduction of the circulating heat transfer fluid 235 may be accomplished by refrigeration system 120. Condenser coil 260 may include a “ref hot gas” connection or connections 265 and liquid connection or connections 270 through which phrase-transition refrigerant 261 of refrigeration system 120 may pass. Couplings between refrigeration system 120 and external air/phase-transition refrigerant heat exchanger or condenser coil 260 are indicated by coupling reference numerals “1” and “2” in FIG. 2. The heat of compression generated in the refrigeration system 120, may be rejected to the process air stream 245 at external air/phase-transition refrigerant heat exchanger or condenser coil 260.

As a result, external air/phase-transition refrigerant heat exchanger or condenser coil 260 may provide variable capacity additional cooling of heat transfer fluid 235 as may be necessary to maintain the proper temperature of heat transfer fluid 235 entering the heat transfer fluid/internal-air heat exchanger 215 to absorb the process heat generated in the cooled volume 105.

Mixing valve 236 may mix heat transfer fluid portion 235A from dry ambient cooling system 115 and heat transfer fluid portion 235B from bypass 230 to provide a combined or mixed flow of heat transfer fluid 235 to refrigeration system 120. Refrigeration system 120 may include compressor 275 coupled with a thermal expansion valve 280 and heat transfer fluid/phase-transition refrigerant heat exchanger 285 to provide cooling of heat transfer fluid 235 that depends on the temperature of the outside or ambient air less than does the operation of dry ambient cooling system 115.

In embodiments, control system 231 may further include temperature sensor 138C to sense the temperature of heat transfer fluid 235 entering air handling unit 110.

Control system 231 may also include dew point sensor 139 to sense a dew point temperature in cooled volume 105 and/or at heat transfer fluid/internal-air heat exchanger 215 and control the heat transfer fluid 235 temperature such that the heat transfer fluid 235 entering the heat transfer fluid/internal-air heat exchanger 215 is above the dew point temperature sensed in the cooled volume 105. This may assure that there is no condensation of water accumulating in the air handling unit 110 or in cooled volume 105 as the heat transfer fluid/internal-air heat exchanger 215 absorbs heat from cooled volume 105, or in the piping and devices transporting the heat transfer fluid 235 between the air handling unit 110 and the dry ambient cooling system 115.

The control system 231 may calculate the coincident process heat absorbing load in the cooled volume 105 based on heat transfer fluid 235 mass flow rate, as may be measured by flow rate sensor 290, and entering and leaving temperatures from heat transfer fluid/internal-air heat exchanger 215. The control system 231 may reset the entering and leaving heat transfer fluid 235 temperatures to provide optimum energy efficient operation for the heat rejection apparatus 115 and 120 while maintaining the capacity required to reject the coincident heat generated in the cooled volume 105.

Control system 231 may control the mass flow rate of the air from fans 240 to adjust heat rejection from of heat transfer fluid portion 235A in heat transfer fluid/external-air heat exchanger 250 when the temperature of the leaving heat transfer fluid portion 235A is sufficient to absorb all of the heat load in heat transfer fluid/internal-air heat exchanger 215. When temperature of the heat transfer fluid portion 235A leaving the heat rejection apparatus 250 reaches the dew point temperature in the cooled volume 105, and when the coincident heat load in the cooled volume 105 is rejected in entirety, control system 231 may use valve 236 to mix heat transfer fluid 235B mass flow rate with heat transfer fluid portion 235A mass flow rate to maintain the required heat transfer fluid temperature entering the heat transfer fluid/internal-air heat exchanger 215 to absorb the coincident heat load in cooled volume 105 and to assure that heat transfer fluid 235 entering air handling unit 110 is above the coincident dew point temperature of the cooled volume 105 as well as the devices and piping through which the heat transfer fluid 235 is transported.

FIGS. 3A and 3B are flow charts illustrating an example of an embodiment of a control system module 300 of a control system of a hybrid dry air cooling system, as may implement control system 130 of FIG. 1, control system 231 of FIG. 2, control system 431 of FIG. 4, and control system 531 of FIG. 5. The control system module 300 may be implemented in computer hardware and software, by instructions programmed in electronic circuits, in firmware, and the like. Control system module 300 may control output, such as actuators, including valves, pumps, electric motors, and the like. Control system module 300 may receive information from input components such as thermometers, humidity or moisture sensors, barometric and liquid pressure sensors, pumps, flow rate sensors, cameras, and the like, as may be illustrated in FIG. 2, FIG. 4, and/or FIG. 5. By way of example, an example of control system module 300 is illustrated in control system computer 600 in FIG. 6.

At block 305 of sheet 3 of 5, FIG. 3A, control system module 300 may measure a temperature, volume, or volumetric flow rate of heat transfer fluid, such as heat transfer fluid entering an internal air cooler, such as heat transfer fluid/internal-air heat exchanger 215/415. Control system module 300 may perform this measurement with data from, for example, temperature sensor 138C/438C/538C.

At block 310, control system module 300 may measure a temperature and/or volume or flow rate of heat transfer fluid, such as heat transfer fluid existing an internal air cooler, such as heat transfer fluid/internal-air heat exchanger 215/415/515. Control system module 300 may perform this measurement with data from, for example, temperature sensor 138B/438B/538B and flow rate sensor 290/490/590 or another flow rate sensor provided for this purpose (with respect to FIG. 2, flow rate at flow rate sensor 290 may be assumed to be the flow rate of heat transfer fluid into heat transfer fluid/internal-air heat exchanger 215; with respect to FIG. 4 and FIG. 5, flow rate at flow rate sensor 491/591 may be the flow rate of heat transfer fluid into heat transfer fluid/internal-air heat exchanger 415/515).

At block 311, control system module 300 may measure a temperature, volume, and/or humidity of return air from a cooled volume. Control system module 300 may perform this measurement with data from, for example, temperature sensor 138D/438D/538D. At block 311, control system module 300 may also measure a temperature and/or humidity of ambient external air, such as with data from temperature sensor 138A/438A/538A.

At block 315, control system module 300 may determine a heat absorption load in the internal air cooler. This may be determined as a change (or delta) in temperature relative to a volume of the heat transfer fluid and/or relative to a volume of air to and from the cooled volume.

In opening loop block 320 to closing loop block 365, control system module 300 may iterate over conditions when a positive heat absorption load occurs in the internal air cooler, such as when cooling is required of return air. These loop blocks may also be performed for a determination of heat absorption load that is presumed to apply for a period of time.

At block 321, which may be optional (such as with a control system which does not modulate overall flow rate of heat transfer fluid), control system module 300 may modulate the flow rate of heat transfer fluid, above a minimum flow rate required for proper system operation. For example, when reduced cooling capacity is required, control system module 300 may control pump 425/525 to reduce flow rate; when increased cooling capacity is required, control system module 300 may control pump 425/525 to increase flow rate.

At block 325, control system module 300 may determine an enthalpy of ambient external air and a cooling capacity of a dry ambient cooling system, such as dry ambient cooling system 115 in FIG. 1.

At decision block 330, control system module 300 may determine whether there is remaining, unutilized, cooling capacity in the dry ambient cooling system.

At block 335, when control system module 300 determines there is not remaining cooling capacity in the dry ambient cooling system or equivalent, control system module 300 may increase a flow rate of heat transfer fluid to a mechanical cooling system and/or control system module 300 may increase a power to the mechanical cooling system, such as refrigeration system 120 in FIG. 1. Control system module 300 may also decrease a flow rate of heat transfer fluid into the dry ambient cooling system.

At block 340, when control system module 300 determines there is remaining cooling capacity in the dry ambient cooling system or equivalent, control system module 300 may reduce a flow rate of heat transfer fluid to the mechanical cooling system. Control system module 300 may also increase a flow rate of heat transfer fluid into the dry ambient cooling system.

At decision block 341, control system module 300 may determine whether ambient external air is cooler or has lower enthalpy than an upper limit of an allowed range for the heat transfer fluid existing the heat transfer fluid/internal air heat exchanger.

At block 342, the determination at decision block 341 was negative or equivalent (ambient external air is not cooler than upper limit), control system module 300 may, at block 344, increase or maintain a flow rate of heat transfer fluid into heat transfer fluid/internal air heat exchanger.

At block 343, the determination at decision block 341 was affirmative or equivalent (ambient external air is cooler than upper limit), control system module 300 may, at block 344, decrease a flow rate of heat transfer fluid into heat transfer fluid/internal air heat exchanger.

In this way, if ambient external air is cooler than the upper limit, then by trimming or decreasing the flow rate of heat transfer fluid into heat transfer fluid/internal air heat exchanger, control system module 300 may thereby increase the temperature of heat transfer fluid exiting the heat transfer fluid/internal air heat exchanger, thereby making it possible for the dry ambient cooling system to provide some cooling.

As noted elsewhere, modulating the flow rate of heat transfer fluid into heat transfer fluid/internal air heat exchanger may be performed by modulating the flow rate of heat transfer fluid in the entire closed loop of heat transfer fluid, thereby increasing or decreasing the flow rate in the entire system. Alternatively and/or in addition, modulating the flow rate into heat transfer fluid/internal air heat exchanger may be performed by modulating the flow rate into heat transfer fluid/internal air heat exchanger, which may result in a bypass of heat transfer fluid external to heat transfer fluid/internal air heat exchanger. Under such circumstances, control system module 300 may modulate the flow rate of heat transfer fluid external to heat transfer fluid/internal air heat exchanger, for example, to decrease the flow rate. The flow rate external to heat transfer fluid/internal air heat exchanger may be kept at or above a minimum threshold required for proper system operation.

Turning to sheet 4 of 5 and FIG. 3B (which continues control system module 300 from FIG. 3A), at block 345, control system module 300 may modulate external air fans, which may serve both the dry ambient cooling system and external air/phase-transition refrigerant heat exchanger or condenser coil 260/460/560, such as to increase or decrease the fans and the volume of ambient external air drawn over heat transfer fluid/external air heat exchanger and the condenser coil. For example, when cooling capacity remains in the dry ambient cooling system and when this cooling capacity is needed or when power is increased to the mechanical cooling system, the fans may be increased.

At block 350, control system module 300 may determine a dew point temperature in the cooled volume, such as according to data received at block 311 or equivalent.

At decision block 355, control system module 300 may determine whether the temperature of heat transfer fluid returning back to heat transfer fluid/internal air heat exchanger is above or below the dew point temperature of block 350.

If the determination at decision block 355 was that the temperature of heat transfer fluid returning back to heat transfer fluid/internal air heat exchanger is below the dew point temperature, at block 360 control system module 300 may reduce cooling of heat transfer fluid (such as via mechanical cooling system and/or dry ambient cooling system) and/or may reduce a flow rate of heat transfer fluid into heat transfer fluid/internal air heat exchanger. This may be performed within an allowed range.

Closing loop block 365 may follow decision block 355 or block 360. Closing loop block 365 may return to opening loop block 320 while a positive load condition obtains or closing loop block 365 may return to block 305.

At block 370, control system module 300 may return to block 305, if a done, exit, or other conclusion condition does not occur.

At block 399, control system module 300 may conclude and/or may return to a process which may have called it.

FIG. 4 is a schematic diagram of a second implementation of components of a hybrid dry air cooling system 400. Hybrid dry air cooling system 400 comprises many of the components of hybrid dry air cooling system 200, generally given the same or a similar name, potentially with a different reference number.

As illustrated in FIG. 4, air handling unit 110 may include one or more blowers or fans 405 that may draw warm return air 410 from within cooled volume 105 (of FIG. 1) across or through a cooling manifold or heat transfer fluid/internal-air heat exchanger 415. Heat transfer fluid/internal-air heat exchanger 415 may be coupled to the closed loop of heat transfer fluid 435 and to the return air 410. Heat transfer fluid/internal-air heat exchanger 415 may thereby cool the return air 410 using heat transfer fluid 435, producing cooled supply air 420. Supply air 420 may then be returned to cooled volume 105 by fans 405, at a temperature lower than return air 410.

Pump 425 may be operated by control system 431 to circulate heat transfer fluid 435 through its closed loop toward dry ambient cooling system 115 and refrigeration system 120. Pump 425 may be operated at a variable flow rate to increase or decrease cooling capacity of the hybrid dry air cooling system. The variable flow rate may be kept above a minimum flow rate required for proper system operation (such as for operation of control valves, heat exchangers, and the like).

Control system 431 in FIG. 4 is illustrated as connecting to output and input components via electrical, data, pneumatic, or physical lines (illustrated with broken lines). Control system 431 is an example of control system 130 in FIG. 1. Control system 431 may be coupled to and control operation of valves 437A-437D. With reference to FIG. 1, mixing valves 437A-437D may operate as mixer 125. For example, mixing valves 437A-437D may be selectively operated by control system 431 so that a heat transfer fluid portion 435A of heat transfer fluid 435 may pass through dry ambient cooling system 115 and/or a heat transfer fluid portion 435B of heat transfer fluid 435 may pass through a bypass 430 that bypasses ambient cooling system 115, as described herein in greater detail. Mixing valve 437B and/or pump 425 may be operated by control system 431 to operate as mass flow rate controller 126, to control the flow rate of heat transfer fluid into air handling unit 110, heat transfer fluid/internal air heat exchanger 415, and heat transfer fluid/phase-transition refrigerant heat exchanger 485 as described further herein.

Control system 431 may include one or more temperature sensors 438A, 438B, 438C, 438D for example, that may provide temperature readings from which control system 431 may control proportional and/or relative operation or use of dry ambient cooling system 115 and refrigeration system 120 and activation of valve 437B and/or pump 425.

Dry ambient cooling system 115 may include one or more blowers or fans 440 that may draw ambient (e.g., outside) external air 445 across or through a heat transfer fluid/external-air heat exchanger 450 (e.g., a heat rejection coil or cooling manifold). Heat transfer fluid/external-air heat exchanger 450 may be coupled to the closed loop of heat transfer fluid 435 to receive heat transfer fluid portion 435A and so may provide cooling of heat transfer fluid 435 that is carrying heat from warmed return air 410 from cooled volume 105 (of FIG. 1). After passing across heat transfer fluid/external-air heat exchanger 450, the ambient external air 445 may be vented out or returned as return ambient air 455. Temperature sensor 438A may sense or measure the temperature of ambient (e.g., outside) external air 445, and temperature sensor 438B may sense or measure the temperature of heat transfer fluid 435 passing out of air handling unit 110.

In some embodiments and/or under some conditions, control system 431 may operate pump 425 to modulate the hybrid system cooling capacity by controlling flow rate of heat transfer fluid 435. For example, when reduced cooling capacity is required, control system 431 may reduce a flow rate of heat transfer fluid 435; when increased cooling capacity is required control system 431 may increase a flow rate of heat transfer fluid 435.

In some embodiments and/or under some conditions, control system 431 may operate mixing valves 437A-437D to direct some or all of heat transfer fluid 435 as heat transfer fluid portion 435A passing through dry ambient cooling system 115 or may operate mixing valves 437A-437D to direct some or all of heat transfer fluid 435 as heat transfer fluid portion 435B passing through bypass 430. For example, control system 431 may operate mixing valves 437A-437D to direct all of heat transfer fluid 435 as heat transfer fluid portion 435B passing through bypass 430 if the temperature or enthalpy of ambient (e.g., outside) external air 445 measured by temperature sensor 438A is greater than the temperature of heat transfer fluid 435 measured by temperature sensor 438B.

Control system 431 may vary the mass flow rate of heat transfer fluid 435 into air handling unit 110, such as by valve 437B and/or pump 425. Control system 431 may do this to increase or decrease the temperature of heat transfer fluid 435 exiting heat transfer fluid/internal air heat exchanger 415. In such case, valve 437B and/or pump 425 may be part of mass flow rate controller 126. As noted, pump 425 and/or mass flow rate controller 126 may also be modulated to vary the cooling capacity of the hybrid cooling system.

In other embodiments and/or under other conditions, control system 431 may operate mixing valves 437A-437D to modulate or trim the proportions of heat transfer fluid portion 435A and heat transfer fluid portion 435B, when the temperature of cooling ambient (e.g., outside) external air 445 measured by temperature sensor 438A is low enough that ambient cooling system 115 has more cooling capacity than is needed to adequately cool heat transfer fluid 435. In these circumstances, for example, flow rate or proportion of heat transfer fluid portion 435A entering ambient cooling system 115 may be increased and the flow rate or proportion of heat transfer fluid portion 435B entering bypass 430 may be decreased as the temperature of ambient (e.g., outside) external air 445 measured by temperature sensor 438A decreases to provide adequate cooling of the coincident process heat load that heat transfer fluid/internal-air heat exchanger 415 absorbs from cooled volume 105. The heat transfer fluid 435 mass flow rate shall be sufficient to cool the coincident process heat load in the cooled volume 105. The heat transfer fluid 435 mass flow rate may also be kept above a minimum required system pressure, for example, for control valve operation.

In embodiments, dry ambient cooling system 115 may further include an optional external air/phase-transition refrigerant heat exchanger 460 (also referred to as a “condenser coil 460”), which may operate when the heat absorbed by the heat transfer fluid 435 in heat transfer fluid/internal-air heat exchanger 415 is not rejected in its entirety by the flow of external air 445 over heat transfer fluid/external-air heat exchanger 450. Control system 431 may control the mass flow rate of external air 445 with fan(s) 440, which may vary the mass flow rate of external air 445 entering i) heat transfer fluid/external-air heat exchanger 450 and ii) external air/phase-transition refrigerant heat exchanger or condenser coil 460.

When the heat transfer fluid portion 435A leaving the heat transfer fluid/external-air heat exchanger 450 is of insufficiently low temperature to absorb the process heat load in the cooled volume 105 transferred by heat transfer fluid/internal-air heat exchanger 415, further required temperature reduction of the circulating heat transfer fluid 435 may be accomplished by control system 431 through use of refrigeration system 120, such as by sending (additional) power to refrigeration system 120. Condenser coil 460 may include a “ref hot gas” connection or connections 465 and liquid connection or connections 470 through which phrase-transition refrigerant 461 of refrigeration system 120 may pass. Couplings between refrigeration system 120 and external air/phase-transition refrigerant heat exchanger or condenser coil 460 are indicated by coupling reference numerals “1” and “2” in FIG. 4. The heat of compression generated in the refrigeration system 120, may be rejected to the process air stream 445 at external air/phase-transition refrigerant heat exchanger or condenser coil 460.

As a result, external air/phase-transition refrigerant heat exchanger or condenser coil 460 may provide variable capacity, additional, cooling of heat transfer fluid 435 as may be necessary to maintain the proper temperature of heat transfer fluid 435 entering the heat transfer fluid/internal-air heat exchanger 415 to absorb the process heat generated in the cooled volume 105.

Mixing valves 437A-437D may mix heat transfer fluid portion 435A from dry ambient cooling system 115 and heat transfer fluid portion 435B from bypass 430 to provide a combined or mixed flow of heat transfer fluid 435 to refrigeration system 120. Refrigeration system 120 may include compressor 475 coupled with a thermal expansion valve 480 and heat transfer fluid/phase-transition refrigerant heat exchanger 485 to provide cooling of heat transfer fluid 435 that depends on the temperature of the outside or ambient air less than does the operation of dry ambient cooling system 115. In embodiments, all of the pumped volume of heat transfer fluid 435 may pass through heat transfer fluid/phase-transition refrigerant heat exchanger 485, with more or less additional cooling capacity being provided by refrigeration system 120 and thermal expansion valve 480.

In embodiments, control system 431 may further include temperature sensor 438C to sense the temperature of heat transfer fluid 435 entering air handling unit 110, and may include a flow rate sensor 490 to sense a fluid flow rate of heat transfer fluid 435.

Control system 431 may also include dew point sensor 439 to sense a dew point temperature in the cooled volume 105 and/or at heat transfer fluid/internal-air heat exchanger 415 and control the heat transfer fluid 435 temperature such that the heat transfer fluid 435 entering the heat transfer fluid/internal-air heat exchanger 415 is above the dew point temperature sensed in the cooled volume 105. This may assure that there is no condensation of water accumulating in the air handling unit 110 or in the cooled volume 105 as the heat transfer fluid/internal-air heat exchanger 415 absorbs heat from the cooled volume 105, or in the piping and devices transporting the heat transfer fluid 435 between the air handling unit 110 and the dry ambient cooling system 115.

The control system 431 may calculate the coincident process heat absorbing load in the cooled volume 105 based on heat transfer fluid 435 mass flow rate, as may be measured by flow rate sensor 290, and entering and leaving temperatures from heat transfer fluid/internal-air heat exchanger 415. The control system 431 may reset the entering and leaving heat transfer fluid 435 temperatures to provide optimum energy efficient operation for the heat rejection apparatus 115 and 120 while maintaining the capacity required to reject the coincident heat generated in cooled volume 105.

Control system 431 may control the mass flow rate of the air from fans 440 to adjust heat rejection from of heat transfer fluid portion 435A in heat transfer fluid/external-air heat exchanger 450 when the temperature of the leaving heat transfer fluid portion 435A is sufficient to absorb all of the heat load in heat transfer fluid/internal-air heat exchanger 415. When temperature of the heat transfer fluid portion 435A leaving the heat rejection apparatus 450 reaches the dew point temperature in the cooled volume 105, and when the coincident heat load in the cooled volume 105 is rejected in entirety, control system 431 may use valves 437A-437D to mix heat transfer fluid 435B mass flow with heat transfer fluid portion 435A mass flow rate to maintain the required heat transfer fluid temperature entering the heat transfer fluid/internal-air heat exchanger 415 to absorb the coincident heat load in cooled volume 105 and to assure that heat transfer fluid 435 entering air handling unit 110 is above the coincident dew point temperature of the cooled volume 105 as well as the devices and piping through which the heat transfer fluid 435 is transported.

Control system 431 may further control valves 437A-437D and in particular, valve 437B, to adjust a flow rate of heat transfer fluid 435 through air handling apparatus 110 and heat transfer fluid/internal-air heat exchanger 415. As discussed herein, maintaining a constant flow rate may result in a temperature of heat transfer fluid 435 exiting heat transfer fluid/internal-air heat exchanger 415 that is below an upper limit of an allowed range for the heat transfer fluid existing the heat transfer fluid/internal air heat exchanger. When ambient external air temperature is below this upper limit, control system 431 may use dry ambient cooling system 115 to provide free energy cooling with reduced use of mechanical refrigeration system 120.

FIG. 5 is a schematic diagram of a second implementation of components of a hybrid dry air cooling system 500. Hybrid dry air cooling system 500 comprises many of the components of hybrid dry air cooling system 200, generally given the same or a similar name, potentially with a different reference number.

As illustrated in FIG. 5, air handling unit 110 may include one or more blowers or fans 505 that may draw warm return air 510 from within cooled volume 105 (of FIG. 1) across or through a cooling manifold or heat transfer fluid/internal-air heat exchanger 515. Heat transfer fluid/internal-air heat exchanger 515 may be coupled to the closed loop of heat transfer fluid 535 and to the return air 510. Heat transfer fluid/internal-air heat exchanger 515 may thereby cool the return air 510 using heat transfer fluid 535, producing cooled supply air 520. Supply air 520 may then be returned to cooled volume 105 by fans 505, at a temperature lower than return air 510.

Pump 525 may be operated by control system 531 to circulate heat transfer fluid 535 through its closed loop toward dry ambient cooling system 115 and refrigeration system 120. Pump 525 may be operated at a variable flow rate to increase or decrease cooling capacity of the hybrid dry air cooling system. The variable flow rate may be kept above a minimum flow rate required for proper system operation (such as for operation of control valves, heat exchangers, and the like).

Control system 531 in FIG. 5 is illustrated as connecting to output and input components via electrical, data, pneumatic, or physical lines (illustrated with broken lines). Control system 531 is an example of control system 130 in FIG. 1. Control system 531 may be coupled to and control operation of valves 536. With reference to FIG. 1, valves 536 may operate as mixer 125. For example, all of heat transfer fluid 535 circulating in the closed loop of heat transfer fluid 535, heat transfer fluid portion 535A, may pass through dry ambient cooling system 115 and heat transfer fluid/external-air heat exchanger 550; valves 536 may be selectively operated by control system 531 such that a heat transfer fluid portion 535B of heat transfer fluid 535 cooled by refrigeration system 120 is mixed with heat transfer fluid portion 535A. Valve 536 and/or pump 525 may be operated by control system 531 to operate as mass flow rate controller 126, to control the flow rate of heat transfer fluid into air handling unit 110, heat transfer fluid/internal air heat exchanger 515, and heat transfer fluid/phase-transition refrigerant heat exchanger 585 as described further herein.

Control system 531 may include one or more temperature sensors 538A, 538B, 538C, 538D for example, that may provide temperature readings from which control system 531 may control proportional and/or relative operation or use of dry ambient cooling system 115 and refrigeration system 120 and activation of valve 536 and/or pump 525.

Dry ambient cooling system 115 may include one or more blowers or fans 540 that may draw ambient (e.g., outside) external air 545 across or through a heat transfer fluid/external-air heat exchanger 550 (e.g., a heat rejection coil or cooling manifold). Heat transfer fluid/external-air heat exchanger 550 may be coupled to the closed loop of heat transfer fluid 535 to receive heat transfer fluid portion 535A and so may provide cooling of heat transfer fluid 535 that is carrying heat from warmed return air 510 from cooled volume 105 (of FIG. 1). After passing across heat transfer fluid/external-air heat exchanger 550, the ambient external air 545 may be vented out or returned as return ambient air 555. Temperature sensor 538A may sense or measure the temperature of ambient (e.g., outside) external air 545, and temperature sensor 538B may sense or measure the temperature of heat transfer fluid 535 passing out of air handling unit 110.

In some embodiments and/or under some conditions, control system 531 may operate pump 525 to modulate the hybrid system cooling capacity by controlling flow rate of heat transfer fluid 535. For example, when reduced cooling capacity is required, control system 531 may reduce a flow rate of heat transfer fluid 535; when increased cooling capacity is required control system 531 may increase a flow rate of heat transfer fluid 535.

In some embodiments and/or under some conditions, control system 531 may operate valves 536 to direct some or all of heat transfer fluid 535 as heat transfer fluid portion 535A passing through dry ambient cooling system 115 or may operate valves 536 to direct some or all of heat transfer fluid portion 535B to mix with heat transfer fluid portion 535A passing through bypass 530, to provide mechanical cooling to heat transfer fluid 535.

Control system 531 may vary the mass flow rate of heat transfer fluid 535 into air handling unit 110, such as by valves 536 and/or pump 525. Control system 531 may do this to increase or decrease the temperature of heat transfer fluid 535 exiting heat transfer fluid/internal air heat exchanger 515. In such case, valves 536 and/or pump 525 may be part of mass flow rate controller 126. As noted, pump 525 and/or mass flow rate controller 126 may also be modulated to vary the cooling capacity of the hybrid cooling system.

In other embodiments and/or under other conditions, control system 531 may operate mixing valves 536 to modulate or trim the proportions of heat transfer fluid portion 535A and heat transfer fluid portion 535B, when the temperature of cooling ambient (e.g., outside) external air 545 measured by temperature sensor 538A is low enough that ambient cooling system 115 has more cooling capacity than is needed to adequately cool heat transfer fluid 535. In these circumstances, for example, flow rate or proportion of heat transfer fluid portion 535A entering ambient cooling system 115 may be increased and the flow rate or proportion of heat transfer fluid portion 535B entering bypass 530 may be decreased as the temperature of ambient (e.g., outside) external air 545 measured by temperature sensor 538A decreases to provide adequate cooling of the coincident process heat load that heat transfer fluid/internal-air heat exchanger 515 absorbs from cooled volume 105. The heat transfer fluid 535 mass flow rate shall be sufficient to cool the coincident process heat load in the cooled volume 105. The heat transfer fluid 535 mass flow rate may also be kept above a minimum required system pressure, for example, for control valve operation.

In embodiments, dry ambient cooling system 115 may further include an optional external air/phase-transition refrigerant heat exchanger 560 (also referred to as a “condenser coil 560”), which may operate when the heat absorbed by the heat transfer fluid 535 in heat transfer fluid/internal-air heat exchanger 515 is not rejected in its entirety by the flow of external air 545 over heat transfer fluid/external-air heat exchanger 550. Control system 531 may control the mass flow rate of external air 545 with fan(s) 540, which may vary the mass flow rate of external air 545 entering i) heat transfer fluid/external-air heat exchanger 550 and ii) external air/phase-transition refrigerant heat exchanger or condenser coil 560.

When the heat transfer fluid portion 535A leaving the heat transfer fluid/external-air heat exchanger 550 is of insufficiently low temperature to absorb the process heat load in the cooled volume 105 transferred by heat transfer fluid/internal-air heat exchanger 515, further required temperature reduction of the circulating heat transfer fluid 535 may be accomplished by control system 531 through use of refrigeration system 120, such as by sending (additional) power to refrigeration system 120 and, as discussed, by using mixing valves 536 to mix heat transfer fluid portion 535B into heat transfer fluid portion 535A. Condenser coil 560 may include a “ref hot gas” connection or connections 565 and liquid connection or connections 570 through which phrase-transition refrigerant 561 of refrigeration system 120 may pass. Couplings between refrigeration system 120 and external air/phase-transition refrigerant heat exchanger or condenser coil 560 are indicated by coupling reference numerals “1” and “2” in FIG. 5. The heat of compression generated in the refrigeration system 120, may be rejected to the process air stream 545 at external air/phase-transition refrigerant heat exchanger or condenser coil 560.

As a result, external air/phase-transition refrigerant heat exchanger or condenser coil 560 may provide variable capacity, additional, cooling of heat transfer fluid 535 as may be necessary to maintain the proper temperature of heat transfer fluid 535 entering the heat transfer fluid/internal-air heat exchanger 515 to absorb the process heat generated in the cooled volume 105.

Mixing valves 536 may mix heat transfer fluid portion 535A from dry ambient cooling system 115 and heat transfer fluid portion 535B from bypass 530 to provide a combined or mixed flow of heat transfer fluid 535 which passes through refrigeration system 120 and heat transfer fluid/phase-transition refrigerant heat exchanger 585. Refrigeration system 120 may include compressor 575 coupled with a thermal expansion valve 580 and heat transfer fluid/phase-transition refrigerant heat exchanger 585 to provide cooling of heat transfer fluid 535 that depends on the temperature of the outside or ambient air less than does the operation of dry ambient cooling system 115. In embodiments, all of the pumped volume of heat transfer fluid 535 may pass through heat transfer fluid/phase-transition refrigerant heat exchanger 585, with more or less additional cooling capacity being provided by refrigeration system 120 and thermal expansion valve 580.

In embodiments, control system 531 may further include temperature sensor 538C to sense the temperature of heat transfer fluid 535 entering air handling unit 110, may include a flow rate sensor 590 to sense a fluid flow rate of heat transfer fluid 535 external to air handling unit 110, and may include a flow rate sensor 591 to sense a fluid flow rate of heat transfer fluid 535 into to air handling unit 110.

Control system 531 may also include dew point sensor 539 to sense a dew point temperature in the cooled volume 105 and/or at heat transfer fluid/internal-air heat exchanger 515 and control the heat transfer fluid 535 temperature such that the heat transfer fluid 535 entering the heat transfer fluid/internal-air heat exchanger 515 is above the dew point temperature sensed in the cooled volume 105. This may assure that there is no condensation of water accumulating in the air handling unit 110 or in the cooled volume 105 as the heat transfer fluid/internal-air heat exchanger 515 absorbs heat from the cooled volume 105, or in the piping and devices transporting the heat transfer fluid 535 between the air handling unit 110 and the dry ambient cooling system 115.

The control system 531 may calculate the coincident process heat absorbing load in the cooled volume 105 based on heat transfer fluid 535 mass flow rate, as may be measured by flow rate sensor 290, and entering and leaving temperatures from heat transfer fluid/internal-air heat exchanger 515. The control system 531 may reset the entering and leaving heat transfer fluid 535 temperatures to provide optimum energy efficient operation for the heat rejection apparatus 115 and 120 while maintaining the capacity required to reject the coincident heat generated in cooled volume 105.

Control system 531 may control the mass flow rate of the air from fans 540 to adjust heat rejection from of heat transfer fluid portion 535A in heat transfer fluid/external-air heat exchanger 550 when the temperature of the leaving heat transfer fluid portion 535A is sufficient to absorb all of the heat load in heat transfer fluid/internal-air heat exchanger 515. When temperature of the heat transfer fluid portion 535A leaving the heat rejection apparatus 550 reaches the dew point temperature in the cooled volume 105, and when the coincident heat load in the cooled volume 105 is rejected in entirety, control system 531 may reduce power to mechanical refrigeration system 120 and/or control system 531 may use valves 536 to reduce mixing of heat transfer fluid 535B with heat transfer fluid portion 535A to maintain the required heat transfer fluid temperature entering the heat transfer fluid/internal-air heat exchanger 515 to absorb the coincident heat load in cooled volume 105 and to assure that heat transfer fluid 535 entering air handling unit 110 is above the coincident dew point temperature of the cooled volume 105 as well as the devices and piping through which the heat transfer fluid 535 is transported.

Control system 531 may further control valves 536 to adjust a flow rate of heat transfer fluid 535 through air handling apparatus 110 and heat transfer fluid/internal-air heat exchanger 515. As discussed herein, maintaining a constant flow rate may result in a temperature of heat transfer fluid 535 exiting heat transfer fluid/internal-air heat exchanger 515 that is below an upper limit of an allowed range for the heat transfer fluid existing the heat transfer fluid/internal air heat exchanger. When ambient external air temperature is below this upper limit, control system 531 may use dry ambient cooling system 115 to provide free energy cooling with reduced use of mechanical refrigeration system 120.

FIG. 6 is a functional block diagram illustrating an example of computer device 600 incorporated with the teachings of the present disclosure, according to some embodiments. Computer device may be used, for example, to implement control system module 300. Computer device 600 may include chipset 655, comprising processor 603, input/output (I/O) port(s) and peripheral device interfaces, such as output interface 640 and input interface 645, and network interface 630, and computer device memory 650, all interconnected via bus 620. Network Interface 630 may be utilized to couple processor 603 to a network interface card (NIC) to form connections with a network, with computer device datastore 601, or to form device-to-device connections with other computers.

Chipset 655 may include communication components and/or paths, e.g., buses 620, that couple processor 603 to peripheral devices, such as, for example, output interface 640 and input interface 645, which may be connected via I/O ports. For example, chipset 655 may include a peripheral controller hub (PCH) (not shown). In another example, chipset 655 may include a sensors hub. Input interface 645 and output interface 640 may couple processor 603 to input and/or output devices that include, for example, user and machine interface device(s) including actuators, motors, a display, a touch-screen display, printer, keypad, keyboard, etc., sensor(s) including temperature sensors, flow rate sensors, actuator sensors, inertial measurement unit, camera, global positioning system (GPS), etc., storage device(s) including hard disk drives, solid-state drives, removable storage media, etc. I/O ports for input interface 645 and output interface 640 may be configured to transmit and/or receive commands and/or data according to one or more communications protocols. For example, one or more of the I/O ports may comply and/or be compatible with a universal serial bus (USB) protocol, peripheral component interconnect (PCI) protocol (e.g., PCI express (PCIe)), or the like.

Processor 603 may include one or more execution core(s), which may be central processing units (“CPUs”) and/or graphics processing units (“GPUs”) one or more registers, and one or more cache memor(ies). Processor 603 may include a memory management unit (MMU) to manage memory accesses between processor 603 and computer device memory 650. In some embodiments, processor 603 may be configured as one or more socket(s); each socket may include one or more core(s), a plurality of registers and one or more cache memor(ies). Each core may be configured to execute one or more process(es) 665 and/or one or more thread(s). A plurality of registers may include a plurality of general purpose registers, a status register and an instruction pointer. Cache(s) may include one or more cache memories, which may be used to cache control system module 300 of the present disclosure.

Computer device memory 650 may generally comprise a random access memory (“RAM”), a read only memory (“ROM”), and a permanent mass storage device, such as a disk drive or SDRAM (synchronous dynamic random-access memory). Computer device memory 650 may store program code for software modules or routines, such as, for example, control system module 300 (illustrated and discussed further in relation to FIG. 3).

Computer device memory 650 may also store operating system 680. These software components may be loaded from a non-transient computer readable storage medium 695 into computer device memory 650 using a drive mechanism associated with a non-transient computer readable storage medium 695, such as a floppy disc, tape, DVD/CD-ROM drive, memory card, or other like storage medium. In some embodiments, software components may also or instead be loaded via a mechanism other than a drive mechanism and computer readable storage medium 695 (e.g., via network interface 630).

Computer device memory 650 is also illustrated as comprising kernel 685, kernel space 695, user space 690, user protected address space 660, and computer device datastore 601.

Computer device memory 650 may store one or more process 665 (i.e., executing software application(s)). Process 665 may be stored in user space 690. Process 665 include one or more other process 665 a . . . 665 n. One or more process 665 may execute generally in parallel, i.e., as a plurality of processes and/or a plurality of threads. Process 665 corresponds to one example of an executing software application.

Computer device memory 650 is further illustrated as storing operating system 680 and/or kernel 685. The operating system 680 and/or kernel 685 may be stored in kernel space 695. In some embodiments, operating system 680 may include kernel 685. Process 665 may be unable to directly access kernel space 695. In other words, operating system 680 and/or kernel 685 may attempt to protect kernel space 695 and prevent access by process 665 a . . . 665 n.

Kernel 685 may be configured to provide an interface between user processes and circuitry associated with computer device 600. In other words, kernel 685 may be configured to manage access to processor 603, chipset 655, I/O ports and peripheral devices by process 665. Kernel 685 may include one or more drivers configured to manage and/or communicate with elements of computer device 600 (i.e., processor 603, chipset 655, I/O ports and peripheral devices).

Computer device datastore 601 may comprise multiple datastores, in and/or remote with respect to computer device 600. Datastore 601 may be distributed. The components of computer device datastore 601 may include data groups used by modules and/or routines, e.g, data and data groups used by control system module 300. The data groups used by modules or routines may be represented by a cell in a column or a value separated from other values in a defined structure in a digital document or file. Though referred to herein as individual records or entries, the records may comprise more than one database entry. The database entries may be, represent, or encode numbers, numerical operators, binary values, logical values, text, string operators, references to other database entries, joins, conditional logic, tests, and similar.

As used herein, the term “module” (or “logic”) may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC), a System on a Chip (SoC), an electronic circuit, a programmed programmable circuit (such as, Field Programmable Gate Array (FPGA)), a processor (shared, dedicated, or group) and/or memory (shared, dedicated, or group) or in another computer hardware component or device that execute one or more software or firmware programs having executable machine instructions (generated from an assembler and/or a compiler) or a combination, a combinational logic circuit, and/or other suitable components with logic that provide the described functionality. Modules may be distinct and independent components integrated by sharing or passing data, or the modules may be subcomponents of a single module, or be split among several modules. The components may be processes running on, or implemented on, a single compute node or distributed among a plurality of compute nodes running in parallel, concurrently, sequentially or a combination, as described more fully in conjunction with the flow diagrams in the figures.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes, equivalents, and modifications that come within the spirit of the inventions defined by following claims are desired to be protected. All publications, patents, and patent applications cited in this specification are herein incorporated by reference as if each individual publication, patent, or patent application were specifically and individually indicated to be incorporated by reference and set forth in its entirety herein. 

1. A hybrid cooling system, comprising: a dry ambient cooling system; a refrigerated cooling system; a process air heat exchanger to exchange heat energy between air of a cooled volume and a heat transfer fluid in a closed loop; the heat transfer fluid to circulate in the closed loop between the dry ambient cooling system, the refrigerated cooling system, and the process air heat exchanger; a cooling mixer coupled between the dry ambient cooling system and the refrigerated cooling system to provide mixing of the heat transfer fluid between the dry ambient cooling system and the refrigerated cooling system; a flow rate controller to vary a rate of flow of the heat transfer fluid into the process air heat exchanger; and a control system coupled to the cooling mixer to control proportional cooling provided by the dry ambient cooling system and the refrigerated cooling system and coupled to the flow rate controller to vary the rate of flow of the heat transfer fluid into the process air heat exchanger to maximize proportional cooling provided by the dry ambient cooling system.
 2. The hybrid cooling system of claim 1, wherein to vary the rate of flow of the heat transfer fluid into the process air heat exchanger to maximize proportional cooling provided by the dry ambient cooling system comprises to maintain the heat transfer fluid exiting the process air heat exchanger at an upper end of an allowed temperature range.
 3. The hybrid cooling system of claim 1, wherein to vary the rate of flow of the heat transfer fluid into the process air heat exchanger comprises to vary at least one of an overall rate of circulation of the heat transfer fluid or a rate of circulation of heat transfer fluid in the process air heat exchanger.
 4. The hybrid cooling system of claim 1 wherein the control system includes at least first and second temperature sensors to sense respective first and second temperatures of the heat transfer fluid before and after the process air heat exchanger, and wherein the proportional cooling provided by the dry ambient cooling system and the refrigerated cooling system is controlled at least in part according the first and second temperatures.
 5. The hybrid cooling system of claim 1 wherein the dry ambient cooling system comprises an ambient air heat exchanger and an ambient air fan, wherein the ambient air fan is to draw an ambient air over the ambient air heat exchanger to exchange heat energy between the heat transfer fluid and the ambient air.
 6. The hybrid cooling system of claim 5 wherein the closed loop is a first closed loop, the ambient air heat exchanger is a first ambient air heat exchanger, the refrigerated cooling system comprises a phase-transition refrigerant in a second closed loop, a phase-transition heat exchanger, and a second ambient air heat exchanger, wherein the phase-transition heat exchanger is to exchange heat between the phase-transition refrigerant in the second closed loop and the heat transfer fluid in the first closed loop, and the second ambient air heat exchanger is to exchange heat energy between the phase-transition refrigerant in the second closed loop and the ambient air.
 7. The hybrid cooling system of claim 6 wherein the second ambient air heat exchanger is downstream from the first ambient air heat exchanger.
 8. The hybrid cooling system of claim 7 wherein the first and second ambient air heat exchangers are in an airspace and the ambient air fan is to draw the ambient air over both the first and second ambient air heat exchangers in the airspace.
 9. A method of performing hybrid cooling with a dry ambient cooling system, a refrigerated cooling system, a process air heat exchanger to exchange heat energy between air of a cooled volume, and a heat transfer fluid in a closed loop, the heat transfer fluid to circulate in the closed loop between the dry ambient cooling system, the refrigerated cooling system, and the process air heat exchanger, the method comprising: with a cooling mixer coupled between the dry ambient cooling system and the refrigerated cooling system, mixing the heat transfer fluid between the dry ambient cooling system and the refrigerated cooling system; with a flow rate controller, varying a rate of flow of the heat transfer fluid into the process air heat exchanger.
 10. The method of claim 9, wherein mixing the heat transfer fluid between the dry ambient cooling system and the refrigerated cooling system is performed to control to proportional cooling provided by the dry ambient cooling system and the refrigerated cooling system.
 11. The method of claim 9, wherein varying the rate of flow of the heat transfer fluid into the process air heat exchanger is performed in order to at least one of maintain the heat transfer fluid exiting the process air heat exchanger at an upper end of an allowed temperature range or modulate the cooling capacity provided to the process air heat exchanger.
 12. The method of claim 9, wherein varying the rate of flow of the heat transfer fluid into the process air heat exchanger comprises varying at least one of an overall rate of circulation of the heat transfer fluid or a rate of circulation of heat transfer fluid in the process air heat exchanger.
 13. The method of claim 9, further comprising receiving respective first and second temperatures of the heat transfer fluid before and after the process air heat exchanger, and controlling proportional cooling provided by the dry ambient cooling system and the refrigerated cooling system at least in part according the first and second temperatures.
 14. The method of claim 9, further comprising drawing an ambient air over an ambient air heat exchanger to exchange heat energy between the heat transfer fluid and the ambient air
 15. The method of claim 14, wherein the closed loop is a first closed loop, the ambient air heat exchanger is a first ambient air heat exchanger, the refrigerated cooling system comprises a phase-transition refrigerant in a second closed loop, a phase-transition heat exchanger, and a second ambient air heat exchanger, wherein the phase-transition heat exchanger is to exchange heat between the phase-transition refrigerant in the second closed loop and the heat transfer fluid in the first closed loop, and the second ambient air heat exchanger is to exchange heat energy between the phase-transition refrigerant in the second closed loop and the ambient air.
 16. The method of claim 15, wherein the second ambient air heat exchanger is downstream from the first ambient air heat exchanger.
 17. The method of claim 16, wherein the first and second ambient air heat exchangers are in an airspace and further comprising using an ambient air fan to draw the ambient air over both the first and second ambient air heat exchangers in the airspace. 